Variable condenser



Aug. 2.7, 1935. (,1 CROSBY 2,012,710

VARIABLE CONDENSER Original Filed Oct. 16, 1931 CAKRIER SOURCE POWE K AMPLlFlERS AND FREQUENCY MULTiPLtERS STATION B STATION A RECEIVING APPARATUS INVENTOR MURRAY 6. SBY' ,unM/L ATTORNEY Patented Aug. 27, 1935 UNITED STATES PATENT OFFICE VARIABLE CONDENSER Delaware Application October 16, 1931, Serial No. 569,144 Renewed January 18, 1935 3 Claims.

This invention relates to improvements in electrical condensers and more particularly to condensers oi the variable type which are adapted for use in communication circuits.

5 An object 01' this invention is to provide a variable condenser which is simple in construction, reliable in operation and highly eillcient.

A more specific object is to provide a condenser which is more easily adaptable to remote and electronic control than those heretofore employed.

In general, this invention contemplates the use of an inertialess variable condenser characterized by the absence of mechanical working 1 parts. This characteristic of the invention is achieved by utilizing a glow discharge tube having a plurality of electrodes between which a stream of electrons is arranged to flow. Encircling the tube and separated from the electrodes there is provided an electrical conducting plate which forms one of the capacitive elements of the glow tube. As potential is applied to the electrodes of the tube, the glow in the tube is arranged to strike and to act, in turn, as one of the plates of the condenser, the capacity of which is varied as the current through the tube is effectively varied.

One advantage of this arrangement is that, due to the absence of mechanical working parts in the condenser, the capacity of the glow tube varies 3 instantaneously and at high speeds in accordance with the variation in potential across the electrodes.

Referring to the drawing, Figures 1 and in. illustrate, in perspective, a variable condenser of 35 the glow tube type constructed in accordance with the principles of this invention; and Figs. 2 and 3 illustrate, diagrammatically, typical circuit arrangements wherein such glow tube-may be employed.

o In Fig. 1 is shown a glow tube 20 comprising a sealed glass envelope within which are located two electrodes ii and i2. This tube, it is to be understood, is only illustrative of any type of glow discharge tube which may be employed and 45 may comprise a neon tube, cathode ray tube or any other suitable electron tube. Encircling the outside of the envelope or bulb is an electrical conducting plate ill made of tinfoil or other suitable material. This plate. if desired, may be 50 mounted within the envelope as shown in Figure 1a. The spacing of the elements of the tube is so arranged that plate I0 and each of the electrodes Ii and I2 form capacitive elements of condenser circuits wherein a capacity exists between 55 plate iii and each of the electrodes. Normally,

when there is no current flowing through the tube between the electrodes ii and i2, this capacity is fixed. The application of a potential across electrodes Ii and I2, however, starts a glow and varies the capacity between the elements, the I glow discharge in such case acting as a con ducting plate. The variation of this glow, due to potential variations between the electrodes causing effective changes in the size of the electronic stream, produces a variation in capacity between 10 plate ill and the electrodes ii and I2.

In Fig. 2 is shown a complete transmitting circuit adapted for phase modulation wherein a glow tube is advantageously employed to vary the tuned output circuit of an amplifier. In this 1 arrangement conductor 6 represents a suitable antenna circuit connected to the transmitting system by suitable power amplifiers and frequency multipliers. The waves to be transmitted by antenna circuit 6 are generated by carrier go frequency source I which is connected by means of a transformer 2 to an amplifier tube 3. The usual tuned circuit in the amplifier arrangement comprises a condenser l and an inductance 5 connected in shunt relation to the condenser. The 25 output circuit of this arrangement is associated with the usual power amplifiers and frequency multipliers which are indicated in conventional form by the rectangular box. Directly connected to the anode of the amplifier tube 3 by means of conductor 2| is the variable condenser or glow tube 20, one electrode I i of which is connected to the anode of modulating tube 9 through resistance l3, and the other electrode I! of which is connected directly to ground. A modulating choke coil connects the plate voltage with the anode of tube 9. A transmitter I which may comprise any suitable input device is employed to produce signal waves which are fed through transformer 8 to the modulator tube 9.

The variable condenser or glow tube, it is to be noted, is connected in series with the plate impedance of the modulator tube 9 but effectively connected in parallel with condenser I. Consequently, any variation of the plate impedance of tube 9, such as may be caused by message waves impinging on the diaphragm of transmitter I, will cause a variation of the effective capacity of the glow tube. This variation of the effective capacity of the glow tube will vary the resultant capacity of the tuned circuit 4, 5 in such manner that the output of the amplifier is phase modulated in accordance with the signal wave.

To those who are skilled in the art it will be obvious that a variable capacity as described herein may be employed to vary the tuning of an oscillator circuit to obtain frequency modulation in a manner similar to that used to obtain phase modulation.

Fig. 3 illustrates a remote control system wherein the glow tube 20 is employed to vary the tuning oi! the receiving circuit at station A. In this circuit a movement of the potentiometer ll at station B will vary the voltage applied distant glow tube at station A over transmission line L. This tube is adapted to vary the resultant capacity of tuned circuit I1, I! in response to a variation in potential caused by a movement oi potentiometer II.

A particular advantage of the glow discharge tube described herein is that it is much simpler and more positive in action. than the usual type oi! variable condenser which employs a condenser shaft and suitable driving means.

It is to be understood that the circuits illustrated and described herein have been selected only for the purpose oi. clearly setting forth the principles involved and that the invention is susceptible of being modified to meet diflerent conditions encountered in its use without departing from the spirit and scope of the invention.

What is claimed is:

l. A variable substantially inertialess condenser comprising, a gaseous discharge tube having spaced electrodes immersed in a gas between which electrodes an electronic stream is designed to pass, and a cylindrical member plate located between said spaced electrodes with its axis lying in the path of said stream to form therewith the plates or a condenser. the capacity 01 which is measured by the intensity of said electron stream.

, 2. A variable condenser comprising, a gaseous discharge tube having spaced electrodes. immersed in a gas between which electrodes an electronic stream is designed to pass, a conducting member located between said electrodes and enclosing the path of said stream to form therewith the plates of a condenser, the capacity of which is measured by the intensity of said electron stream, leads passing through the walls of said tube to said spaced electrodes to apply thereto varying potentials which in turn vary the intensity of said electron stream, and leads connected to one of said electrodes and to said plate for applying the capacity variations produced between said stream and said plate to a utilization circuit.

3. A variable substantially inertialess condenser comprising, a gaseous discharge tube having spaced electrodes immersed in a gas between whichelectrodes an electronic stream is designed to pass, and a conducting plate located on the outside of said tube adjacent the path of said stream to form therewith the plates of a condenser, the capacity oi which is measured by the intensity of said electronic stream.

MURRAY G. CROSBY.

-Patent No; 2,012,710.

CERTIFICATE OF CORRECTION.

MURRAY G. CROSBY- It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, i t column, line 33, claim 1, strike out the word "plate"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day May, A. D. 1936.

Leslie Frazer (Seal) Acting Commissioner of Patents.

August 27, 1955.

- Patent No. 2,012,710.

CERTIFICATE OF CORRECTION.

MURRAY G. CROSBY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page i st column, line 33, claim 1, strike out the word "plate" and.- that the said Letters Patent should be read with these corrections ,therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day May, A. D. 1956.

Leslie Frazer (Seal) Acting Commissioner of Patents August 27, 1955. 

